Maths help

Have a look at: http://www.bbc.co.uk/education/guides/ztwmtfr/revision/4 (circle theorem)

and note that the two lines are parallel.

I understand how to work out k, but not i or j. Which rule do you use for the parallel lines? Is it co-interior angles or something?

I understand how to work out k, but not i or j. Which rule do you use for the parallel lines? Is it co-interior angles or something?

Yes, co-interior angles is right

Well, I thought that meant that the angles next to eachother would add to 180? But the answer sheet says that i is 72 and j is 108 (so the ones which are next to eachother are equal). Or am I an idiot and the ones next to eachother are equal?

Well, I thought that meant that the angles next to eachother would add to 180? But the answer sheet says that i is 72 and j is 108 (so the ones which are next to eachother are equal). Or am I an idiot and the ones next to eachother are equal?

Because the lines are parallel, j+72=180

Draw a line through the centre of the circle perpendicular to the parallel lines.

What can you say about the angles (i, 72) and (j, k) now?

There is no need to add an additional line as there is a cyclic quadrilateral ...

The simplest way of doing this will vary with what the OP knows. I was just trying to show the symmetry.

The symmetry only exists because of the cyclic quadrilateral ,,,

That's not how I see it, but whatever works. To me, symmetry is the simpler concept.